Input Devices
Mouse
An LED light is beamed to the surface beneath the mouse which is reflected to a CMOS sensor which calculates the movement on an x-y axis which corresponds to the cursor on the screen.
Voice Recognition
The computer converts the analog signal from a voice into bits of digital data that the computer can analyze and then guess the word. .
Graphics Table
The tablet picks up the information in the pens tip from sensors behind the screen in order to determine the position and other information like pressure. Since the grid provides the power to the pen, you don't need batteries for the pen. There can also be lasers across the screen to determine position and pressure.
Digital Camera
It uses lenses to focus light to create an image, it focuses it to a semiconductor device which turns it into electrical data that a computer can use to turn into digital data and an image.
Keyboard
They electrical parts of a keyboard scan the keys to see if they have been pressed they send a key scan code to the computer which interprets it and puts it on the screen
Smart Card Reader
This reader picks up the binary message in the embedded integrated circuit and reads its content which is usually encrypted for the individual user/business.
Magnetic Strip Reader
The strip on a bank card or I.D can be read by and electromagnet which activates when the card is slid down it. It tells the computer what it is and the other info about the product is stored in a separate database.
Radio Frequency Identification Reader
Objects will give out a radio frequency wave that will be picked up by a Radio Frequency Identification Reader. The two devices need no physical or electrical contact to transfer data.
Optical Mark Reader
A form is put under a light sensor which reflects light off the paper and it senses the degree of intensity that it is reflected back at. the computer then converts it into digital data.
Optical Character Recognition
Optical Character Recognition systems use scanners to input images of text that is then analysed as digital data which is then used to recognise the characters.
Fingerprint Scanner
A bright light scans your fingerprint picking up tiny details which it turns into a digital image. The scanner then changes this digital image into a fingerprint code which is saved and used when the device is activated.
Retina/Iris Scanner
Works by taking scans of parts of the eye which it then analyses and turns into a mathematical
representation of the eye.
Flatbed Scanner
A pane of glass covers the components of the scanner. Sensors below this pane contain shades of blue, green and red. The sensors run along the object detecting the levels of intensity of the light being reflected. This is then used to make up the image.
Output Devices
Cathode Ray Tube Monitor
A CRT contains a cathode. It consists of a thick, heated wire that is contained within a glass tube. This tube is vacuum-sealed to stop resistance. The cathode gives out a stream of electrons into the tube, which travel down. After the electrons are sped up to extremely high speed, they hit a phosphorescent screen at the end of the tube which causes it to glow.
Color television screens use three electron beams at once. They use one each for red, blue and green. These three colors are used in the phosphor coating on of the picture tube. When each color is struck by its electron beam, it glows and creates a color picture. The human eye has been trained into assembling these small dots into a clearer picture. Obviously the more dots per inch, the higher the resolution and the clearer the picture. The highest quality pictures may consist of hundreds of thousands of "dots per inch" creating an extremely clear picture.
Liquid Crystal Display
An LCD screen is made of two pieces of polarized glass which has a Liquid Crystal material between them. A backlight shines light thrugh the first layer of lglass while electrical currents control the levels of light which pass throgh the second that creates the images we see.
Plasma Screen
Plasma TVs use thousands of sealed, low pressure glass chambers filled with a mixture of neon and xenon. Behind these chambers are coloured phosphors, one red, one blue, and one green for each chamber. When heated, these chambers give out invisible UV light. The UV light strikes the red, green and blue phosphors on the back glass of the display making them produce visible light.
Inkjet Printer
This printer sprays ink at high speeds, the printer software has to first process the command. The printer then sprays the paper using dozens of nozzles which print words/images line by line.
When a text or image is entered into the Computer, it many varying voltages. This controls a LED in the printer. This emitts flashes of laser, when it falls on a charged photoconducting drum. The area corresponding the text or image will either be neutrilized or oppisitly charged. A toner which has the same charge as the background is sprayed onto it. It only sticks to the text or image and is repelled by the background. A fresh paper is now pressed onto the toner and is slighlty heated so that it sticks on the paper.
